Background & Objectives: The purpose of this study was to investigate the association between exposure to secondhand smoke (SHS) and length of intensive care unit (ICU) stay in adolescents after scoliosis surgery. Materials & Methods: This prospective observational study randomized controlled double-blinded study was conducted in 113 patients, 12–18 years, with idiopathic scoliosis for elective posterior spinal fusion. All patients underwent standard total intravenous anesthesia and epidural morphine with PCA. The patients were divided into three groups: Group S; consisted of smokers, Group SHS; consisted of exposure smokers, and Group NS; consisted of individuals who did not have any history of smoking and were not exposed to smoke. Information was reported in questionnaires and took blood samples for analysis of serum cotinine. Demographic and clinical characteristics included morphine usage, length of ICU stay and duration of mechanical ventilation were recorded. Results: In the observational period, we were able to include 103 patients in the study. The patient characteristics did not differ between the groups. There was a statistically significant difference among groups in terms of serum cotinine levels. There were no significant differences in VAS and RASS scores between the groups. Morphine consumption was significantly less in Group PS compared with that of Group S at all time points. The median length of ICU stay was longer among the PS than NS groups postoperatively (5 and 3 days/patient, respectively; p=.027). Postoperative nausea-vomiting were significantly decreased in Group S. Conclusion: To the best of our knowledge, this is the first report of the clinical relationship between PS and length of ICU admission scoliosis surgery patient. We found that PS was associated with increased length of ICU stay among scoliosis surgery patient. We concluded that it is important to avoid PS before at ICU admission when possible.